1. Field of the Invention
The present invention relates to an exhaust apparatus for four wheeled vehicle. More specifically, the present invention relates to an exhaust apparatus which is mounted on a utility vehicle mainly suitable for driving on irregular ground and discharges exhaust gas from an engine.
2. Description of the Related Art
Conventionally, an exhaust gas sensor that senses a particular ingredient in exhaust gas is attached to exhaust pipes. Since high-temperature exhaust gas flows in the exhaust pipes, the surfaces of the exhaust pipes and the atmosphere around the exhaust pipes become hot. Therefore, the exhaust gas sensor attached to the exhaust pipes is required to have high heat resistance.
The exhaust gas sensor is provided with a sensor body including a sensing portion that senses a particular ingredient in exhaust gas, and a harness for supplying electric power to the sensor body and transmitting a signal outputted from the sensor body, wherein a connecting portion of the sensor body and the harness includes a bush member that holds air-tightness in the connecting portion. The bush member is formed of a material having flexibility, e.g., rubber, and adopts heat-resistant rubber to withstand a high-temperature atmosphere.
Here, typically, the engine of the utility vehicle which is driven on irregular ground is mounted in a space which is in the center or rear position in the front-rear direction of the vehicle and is in the high position, e.g., below the seat or in a space which is in the console box arranged between the left and right seats and is surrounded at its bottom by the under cover, so as to be unlikely to be affected by an obstacle on the ground. The exhaust pipes connected to the engine are arranged in a rear space which is connected to the rear portion of the space and surrounded by e.g., the heat insulating plate and the under cover. As a result, the exhaust gas sensor attached to the exhaust pipes is also located in the rear space which is away from the front portion of the vehicle and surrounded by the heat insulating plate and the under cover.
The rear space is blocked at its front by the engine. Traveling wind from the front portion of the vehicle is thus unlikely to reach the rear space. In addition, the inside of the rear space is surrounded at its left, right, top, and bottom by the heat insulating plate and the under cover. Traveling wind from the sides or bottom of the vehicle is also unlikely to reach the rear space. Further, the inside of the rear space is brought into a high-temperature atmosphere by heat radiated from the surfaces of the exhaust pipes arranged therein. Consequently, the exhaust gas sensor located in the rear space is required to have higher heat resistance. The bush member having a high allowable temperature is thus adopted. As a result, the cost of the exhaust gas sensor is increased.
To reduce the temperature of the exhaust gas sensor attached to the exhaust pipes, it has been known that a guide member is provided which guides traveling wind taken in from the front portion of the vehicle to the exhaust gas sensor arranged in the front portion of the vehicle. As the prior art document, there is Japanese Unexamined Patent Publication No. 2012-127202.
However, as described above, in the utility vehicle, the exhaust gas sensor is located away from the front portion of the vehicle, and is arranged behind the engine. It is thus difficult to guide the traveling wind from the front portion of the vehicle to the exhaust gas sensor located behind the engine by the guide member, which is described in the prior art document.